Dicyclopentadiene (DCPD) is a relatively plentiful diunsaturated monomer with a variety of potential uses due to the ease of making derivatives by reaction with the double bonds. Its source is the bottoms of light hydrocarbon distillation columns wherein it is formed by prolonged heating of the C.sub.5 fraction. It has the following structure ##STR2##
Reactions are known to form the nitrile or dinitrile by reacting the double bonds of DCPD with HCN; the nitrile can then be hydrolyzed to form the carboxylic acid derivative. The DCPD can also be catalytically reacted with HCN, followed by reduction to obtain the bis methylamine derivative; this product in turn can be reacted with glycolonitrile in the presence of caustic to give the sodium salt of tetraacetic acid of the bis amine, a likely chelating agent since it resembles EDTA.
It is well known that amines such as ethylenediamine and diethylenetriamine can be reacted with formaldehyde and phosphorus acid to obtain methylene phosphonate derivatives of the amine in which the methylene phosphonate group ##STR3## substitutes for the amine hydrogens (U.S. Pat. No. 3,288,846).
The use of methylenephosphonic acid substituted alkylene polyamines for metal ion control at less than stoichiometric amounts was suggested in a patent (U.S. Pat. No. 2,609,390) issued in 1952. Later a water dispersible polymeric amine chelating agent which included alkylene phosphonate derivatives was indicated as having "threshold" effects in scale inhibition applications (see U.S. Pat. No. 3,331,773), this term being used to describe the use of the agent in less than stoichiometric amounts. The diamine and polyamine methylenephosphonate derivatives are taught and claimed in U.S. Pats. Nos. 3,336,221 and 3,434,969, respectively. Some of the products disclosed in these two patents are available commercially and are recommended as scale inhibitors when applied in threshold amounts.
Other patents which disclose heterocyclic nitrogen containing compounds which are useful as chelating agents and may be employed in threshold amounts are U.S. Pat. Nos. 3,674,804; 3,720,498; 3,743,603; 3,859,211; and 3,954,761. Some of the compounds included therein are heterocyclic compounds having the formulas: ##STR4## wherein R is hydrogen or alkyl and M is hydrogen, alkali metal, ammonium or a di- or triethanolamine radical; ##STR5##
Methylenephosphonates of polyalkylene polyamines, disclosed in U.S. Pat. No. 4,051,110, are made by reacting di- or polyamines with a chain extending agent such as a dihalide or an epoxyhalide, e.g. ethylene dichloride or epichlorohydrin and thereafter, with phosphorous acid and formaldehyde. Thus, for example, triethylenetetramine is reacted with epichlorohydrin in an approximately one to one mole ratio; thereafter the product is reacted with phosphorous acid, and formaldehyde in the presence of hydrochloric acid. The resulting methylenephosphonated polyamine is useful in small amounts as scale inhibitor, being employed at concentrations of 20-50 ppm.
Certain phosphonic acid derivatives of the aliphatic acids can be prepared by reacting phosphorous acid with acid anhydrides or acid chlorides, e.g. the anhydrides or chlorides of acetic, propionic and valeric acids. The compounds prepared have the formula ##STR6## wherein R is a lower alkyl radical having 1 to 5 carbon atoms. The method of making and use of these products is described in U.S. Pat. No. 3,214,454. The use of threshold amounts to prevent calcium precipitation is disclosed and claimed therein.
It has now been discovered that new chelating and threshold agents for inhibiting precipitation of metal ions can be made from the bis(methylamine) derivatives of dicyclopentadiene. They can also be considered as tricyclodecane derivatives. Thus, dicyclopentadiene bis(methylamine) can be named 3(4), 8(9)-bis(aminomethyl)tricyclo[5.2.1.0.sup.2,6 ]decane.